Computer-intensive processing of reflection seismic data is the main tool for imaging the Earth's subsurface to identify hydrocarbon reservoirs and determine rock and fluid properties. Seismic data are recorded at the earth's surface or in wells, and an accurate model of the underlying geologic structure is constructed by processing the data. In the past decade, 3-D seismic processing has shown far superior cost-effectiveness than conventional 2-D seismic processing. However, the reconstruction of accurate 3-D images of the subsurface requires the handling of a huge amount of seismic data (on the order of terabytes for a single modern marine 3-D survey) and the application of computer-intensive imaging algorithms. Even today, only large-scale parallel computers can image modern marine surveys with the most sophisticated algorithms within a useful turn-around time. Indeed, the use of large-scale parallel computers for seismic processing has achieved such technical and economical success that the geophysical market accounts for one of the largest commercial market for scientific high-performance computing.
Many exploration organizations have no direct access to high-end seismic imaging technologies because they lack the resources to acquire and maintain the necessary hardware and software. The cost of the required computing and data-storage facilities is still quite high, although it keeps going down. However, in perspective, even more problematic is the large investment in application development and system maintenance that the effective use of these computational facilities requires. These costs are not decreasing, they are actually increasing with the level of complexity and sophistication of the imaging applications. Many existing commercial packages are targeted to run effectively on workstations, not on large parallel systems, and thus are ineffective for the high-end applications. As a result, only the central processing departments of large oil companies can afford to employ large-scale parallel computers for imaging 3-D seismic data. The rest of the exploration industry outsources large 3-D seismic imaging projects to outside service companies.
According to this outsourcing model, the data are physically sent on tape to the service companies, who process the data with little input from the oil companies, and then deliver the final images after several months. This service model has been historically successful for exploring areas with relatively simple geology, but it has proven inadequate for exploring areas with complex geology, where most of the still undiscovered hydrocarbon reservoirs are yet to be found. In such areas, the data must often be imaged by applying 3-D prestack depth migration, instead of simpler and more traditional time imaging procedures. Depth imaging is potentially much more accurate than time imaging, but it is also less robust with respect to some of the processing parameters. In particular, depth imaging needs an accurate interval velocity function to properly focus the reflections. Because the velocity function cannot be uniquely determined from the data alone, a priori geological information must be taken into account, and the final results are greatly enhanced when geologists work closely with the processing team. However, in the typical interaction between service companies and oil companies, the geologist cannot be involved in the processing because of the physical distance and the difficulties caused by the old traditional service model.